Yep, the targa is good for cruising, but you get a bit of "scuttle shake" while punting it on bumpy roads. It's a little disconcerting at first, but you got to know what you want out of the car, and what faults will at niggle you. My targa top Auto (original import) JZA-70 will do me fine - I'm too lazy to shift the gears (the auto probably shifts faster than I could anyway). Also, you get a more reliable launch.
I don't think I've seen aerotop JZA-70's in manual trans though.
There are people in WA who were importing them from Japan. They may have some still, or may be able to help you. I think they are called "Melville Auto Imports" - look up their telephone using White Pages on the net. It would certainly save you heaps of trouble unless you like doing conversions.